Magnetic tunnel junctions and methods of forming magnetic tunnel junctions转让专利
申请号 : US14989556
文献号 : US09691817B2
文献日 : 2017-06-27
发明人 : Gurtej S. Sandhu
申请人 : Micron Technology, Inc.
摘要 :
权利要求 :
The invention claimed is:
说明书 :
This patent resulted from a divisional application of U.S. patent application Ser. No. 14/023,138, filed Sep. 10, 2013, entitled “Magnetic Tunnel Junctions And Methods Of Forming Magnetic Tunnel Junctions”, naming Gurtej S. Sandhu as inventor, the disclosure of which is incorporated by reference.
Embodiments disclosed herein pertain to magnetic tunnel junctions and to methods of forming magnetic tunnel junctions.
A magnetic tunnel junction is an integrated circuit component having two magnetic materials separated by a thin non-magnetic dielectric material. The dielectric material is sufficiently thin such that electrons can tunnel from one magnetic material to the other through the dielectric material under appropriate conditions. At least one of the magnetic materials is ferromagnetic whereby its magnetic domain direction can be switched between two states, and is commonly referred to as the “free” or “recording” material. The other material may not be ferromagnetic, and may commonly be referred to as the “reference” or “fixed” material. The reference material and the recording material are electrically coupled to respective conductive nodes. The resistance of current flow between those two nodes through the reference material, dielectric material, and recording material is dependent upon the magnetic domain direction of the recording material relative to that of the reference material. Accordingly, a magnetic tunnel junction can be programmed into one of at least two states, and those states can be sensed by measuring current flow through the magnetic tunnel junction. Since magnetic tunnel junctions can be “programmed” between two current-conducting states, they have been proposed for use in memory integrated circuitry. Additionally, magnetic tunnel junctions may be used in logic or other circuitry apart from or in addition to memory.
The magnetic domain direction of the recording material can be switched by an external magnetic field or by using a spin-polarized current to result in a spin-transfer torque effect. Charge carriers (such as electrons) have a property known as “spin” which is a small quantity of angular momentum intrinsic to the carrier. An electric current is generally unpolarized (having 50% “spin-up” and 50% “spin-down” electrons). A spin-polarized current is one with more electrons of either spin. By passing a current through magnetic material, one can produce a spin-polarized current. If a spin-polarized current is directed into a ferromagnetic material, angular momentum can be transferred to that material, thereby affecting its orientation. This can be used to excite oscillations or even flip (i.e., switch) the orientation/domain direction of the ferromagnetic material.
Typical existing proposals for magnetic tunnel junctions form the two magnetic materials and non-magnetic material as a pillar, for example that may have circular or rectangular horizontal cross-section. Those configurations are typically created by depositing a stack of the three materials, followed by etching the stack to form a plurality of magnetic tunnel junctions which individually include the three materials. Unfortunately, etching of such materials can cause damage to the sidewalls/edges of the resultant pillars. This damage can be sufficient to adversely affect device operation, particularly as the pillars become smaller and narrower.
Example methods of forming a line or lines of magnetic tunnel junctions in accordance with some embodiments of the invention are initially described with reference to
Any of the materials and/or structures described herein may be homogenous or non-homogenous, and regardless may be continuous or discontinuous over any material which such overlie. As used herein, “different composition” only requires those portions of two stated materials that may be directly against one another to be chemically and/or physically different, for example if such materials are not homogenous. If the two stated materials are not directly against one another, “different composition” only requires that those portions of the two stated materials that are closest to one another be chemically and/or physically different if such materials are not homogenous. In this document, a material or structure is “directly against” another when there is at least some physical touching contact of the stated materials or structures relative one another. In contrast, “over”, “on”, and “against” not preceded by “directly”, encompass “directly against” as well as construction where intervening material(s) or structure(s) result(s) in no physical touching contact of the stated materials or structures relative one another. Further, unless otherwise stated, each material may be formed using any suitable or yet-to-be-developed technique, with atomic layer deposition, chemical vapor deposition, physical vapor deposition, epitaxial growth, diffusion doping, and ion implanting being examples.
Referring to
Electrically conductive vias 24 are shown extending through the insulator material of outer regions 16 between immediately adjacent outer regions 14. Vias 24 will individually electrically couple with the magnetic tunnel junctions being formed as will be apparent from the continuing discussion. Conductive vias 24 may be of any suitable configuration, and may be of the same, lesser, or greater maximum lateral dimension as outer regions 14 of the reactant source material. Other partially or wholly fabricated components of integrated circuitry may be formed as a part of or be elevationally inward of vias 24 and the material of outer regions 14, 16 (e.g., CMOS devices and at least one level of interconnections), and are not particularly germane to the inventions disclosed herein.
Referring to
The reactant source material of outer regions 14 comprises a reactant that will react with magnetic recording material 26 to form dielectric material when subjected to a set of temperature and pressure conditions. Ideally, the insulator material of outer regions 16 is not reactive with magnetic recording material 26 to form such dielectric material when subjected to the set of temperature and pressure conditions, or at least is not as reactive with magnetic recording material 26 as is the reactant source material. In one embodiment, the set of temperature and pressure conditions are ambient room temperature to about 350° C., and greater than about 10 Torr, respectively (in argon gas, for example). In one embodiment, temperature of the set of temperature and pressure conditions is at least 50° C. In one embodiment, the reactant comprises oxygen (i.e., elemental oxygen and/or oxygen-containing radicals, ions, molecules, etc.), for example to form dielectric metal oxide(s). Specific example such reactant source materials include at least one of silicon dioxide and an aluminum oxide. In one embodiment, the reactant comprises nitrogen (i.e., elemental nitrogen and/or nitrogen-containing radicals, ions, molecules, etc.), for example to form dielectric metal nitride(s). Specific example such reactant source materials include at least one of a silicon nitride and a boron nitride.
In one embodiment, the reactant source material comprises one of a dielectric nitride and a dielectric oxide, and the insulator material comprises the other of dielectric nitride and dielectric oxide. As examples, one of the reactant source material and the insulator material comprises silicon dioxide and the other comprises silicon nitride. However, embodiments of the invention encompass the reactant source material and the insulator material each comprising like-materials, for example each comprising silicon dioxide or each comprising silicon nitride. As examples, where the reactant is one of oxygen or nitrogen, different techniques of deposition may result in slightly different silicon dioxides or silicon nitrides, respectively, wherein one more readily gives up oxygen or nitrogen, respectively, than does the other of silicon dioxide or silicon nitride, respectively. As examples with respect to silicon dioxide deposition, deposition techniques using ozone and tetraethylorthosilicate (TEOS), plasma and TEOS, spin-on-glass, or CVD using silane, may result in materials which more readily give up oxygen as compared to silicon dioxides using TEOS as a silicon dioxide deposition precursor in the absence of any ozone.
Regardless, in one embodiment, the reactant source material comprises a stoichiometric compound having a stoichiometric formula (e.g., one or both of SiO2 and Si3N4). The reactant comprises an atom of the formula (e.g., O and/or N), and the reactant source material is deposited to comprise an excess of a stoichiometric amount of the atom in the formula. For example, silicon dioxide and/or silicon nitride may be deposited to have an excess of the stoichiometric amount of oxygen and nitrogen which may facilitate amount of reactant available for reaction with recording material 26.
Referring to
In one embodiment and as shown, non-magnetic material 27 has also been etched to be longitudinally elongated with and form part of longitudinally elongated line 30 of magnetic reference material 28. Further in one embodiment and as shown, magnetic recording material 26 has also been etched to be longitudinally elongated with and form a part of longitudinally elongated line 30 of magnetic reference material 28. However, in another embodiment, a method in accordance with the invention is devoid of etching of the recording material, with example such embodiments being further described below.
Referring to
Additional embodiments of a method of forming a line or lines of magnetic tunnel junctions are next described with reference to
Referring to
Referring to
Referring to
Any other attribute as described above with respect to the embodiments of
Embodiments of the invention also encompass a line of magnetic tunnel junctions independent of the method of manufacture. Nevertheless, a line of magnetic tunnel junctions may have any of the structural attributes as shown and described above with respect to
The non-magnetic material may be longitudinally continuous along the line, for example as is shown in each of the embodiments of
In one embodiment, the non-magnetic material may extend laterally beyond those longitudinal edges (e.g., the embodiments of
In some embodiments, a method of forming a line of magnetic tunnel junctions comprises forming magnetic recording material over a substrate, non-magnetic material over the recording material, and magnetic reference material over the non-magnetic material. The substrate comprises alternating outer regions of reactant source material and insulator material along at least one cross-section. The reactant source material comprises a reactant that will react with the recording material to form dielectric material when subjected to a set of temperature and pressure conditions. The reference material is patterned into a longitudinally elongated line passing over the alternating outer regions. The recording material is subjected to the set of temperature and pressure conditions to react with the reactant of the reactant source material to form regions of the dielectric material which longitudinally alternate with the recording material along the line and to form magnetic tunnel junctions along the line which individually comprise the recording material, the non-magnetic material, and the reference material that are longitudinally between the dielectric material regions.
In some embodiments, a method of forming lines of magnetic tunnel junctions comprises forming magnetic recording material over a substrate, non-magnetic material over the recording material, and magnetic reference material over the non-magnetic material. The substrate comprises islands of outer regions of insulator material within an expanse of outer reactant source material. The reactant source material comprises a reactant that will react with the recording material to form dielectric material when subjected to a set of temperature and pressure conditions. The reference material is etched to form a plurality of longitudinally elongated lines of the reference material that individually pass over respective pluralities of different ones of the islands. The recording material is not etched to form lines within the expanse. The recording material is subjected to the set of temperature and pressure conditions to react with the reactant of the reactant source material to form regions of the dielectric material which longitudinally alternate with the recording material along individual of the lines and to form magnetic tunnel junctions along individual of the lines which individually comprise the recording material, the non-magnetic material, and the reference material that are longitudinally between the dielectric material regions.
In some embodiments, a line of magnetic tunnel junctions comprises magnetic recording material and magnetic reference material having non-magnetic material there-between. The reference material is longitudinally continuous along the line. The line comprises regions of dielectric material which longitudinally alternate with the recording material along the line. The magnetic tunnel junctions individually comprise the recording material, the non-magnetic material, and the reference material that are longitudinally between the dielectric material regions along the line.
In compliance with the statute, the subject matter disclosed herein has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the claims are not limited to the specific features shown and described, since the means herein disclosed comprise example embodiments. The claims are thus to be afforded full scope as literally worded, and to be appropriately interpreted in accordance with the doctrine of equivalents.